The aim was to produce a child's toy that would behave subtly but deterministically as it was moved. Different qualities of light produce different sounds. 100Hz modulated mains sources cause a different sound from unmodulated sources.
We started with an initial sketch of the design
We tested out the circuit in mid air. It makes a quiet sound using the blue piezo sounder. Two photodiodes control two coupled multi-vibrator oscillators, one for audio and the other for LFO FM modulation. Three leds and a tilt switch complete the system.
Some hardwood taken from a phutong was used as the skeleton and the battery holder was cut out of the core. An inlayed slot at the top takes the button switches.
A 3.5 mm jack socket was fitted on the back to allow headphones to be connected.
The lower skin covering was glued on early on.
Holes through the body of the timber allow wires to run between the separate compartments.
The left half of the arrowhead contains the mechanical tilt switch and the audio-frequency oscillator. One LED is connected to the tilt switch and the other to the modulation source. A photodiode provides frequency modulation.
The right half of the arrowhead contains the LFO multivibrator and its photodiode that controls its rate.
The tail fin contains a piezo sounder and the on/off control and the headphone amplifier.
The chambers were filled with hotmelt glue to secure the parts and add strength.
The rear battery catch is held in place with one, deeply-recessed screw.
The buttons were turned from sections of dowle.
An inset piece of wood, flush with the hardwood body, retains the buttons over the switches.
Each button causes the device to turn on while pressed and one of them leaves it on for a number of seconds. While pressed, each button puts the electronics into a slightly different mode.
Finally, the top cover was glued on.
Varnishing and Finishing Off
The excess timber from the top and bottom covers was trimmed off and then all the corners were shamfered. The whole unit was sanded down to remove any sharp edges. Then a thin-layer of varnish was applied. Note that some varnishes are specially recommended as suitable for children's toys.
The finished item. A crude hole in each side of the tail fin lets the sound out.
In the future we might make some more of these. They could have a microphone in them to pick up noise and react to it. Or perhaps pairs of them could interact with each other using infra-red beams. Of course, a printed-circuit board could be used to reduce assembly costs.
Copyright (C) 2002 Mixerton. Mixerton ST. All rights reserved.